1. Field of the Invention
The present invention relates to a composite writing utensil which houses any plural writing shafts such as, for example, a ballpoint pen writing shaft, a mechanical pencil writing shaft, an eraser writing shaft, and a writing shaft for computer input, and in which a point of one writing shaft of the plural writing shafts can selectively be projected from a point aperture of a barrel, and more particularly to a composite writing utensil which is small in the outer diameter of the barrel.
2. Description of the Related Art
Conventionally, a composite writing utensil of this type is typically required to house a plurality of writing shafts and a mechanism for selectively projecting one of them within a barrel, and consequently has the barrel which is large in its size and diameter.
In contrast, composite writing utensils which are small in diameter are described in Japanese Utility Model Laid-Open Nos. 61-140887 and 55-47362.
In the structure described in the Japanese Utility Model Laid-Open No. 61-140887, a knock rod coupled to a rear end portion of each writing shaft is movable along a window hole formed in the rear portion of the writing shaft, and any writing shaft can selectively be used by advancing a knock rod coupled to the rear end portion of a writing shaft to be projected along the window hole. During the operation, the knock rod and the writing shaft move substantially linearly along the axial direction of the barrel.
Also, in the structure described in the Japanese Utility Model Laid-Open No. 55-47362, a slider is provided within the barrel, a swinging pendulum is coupled to the slider, and further, the slider is provided with a projection pin so as to project in the radial direction. Urging a rear-end knock button makes the slider advance, the projection pin of the slider engage with a return button provided on a clip, and a tip of the swinging pendulum engage with any writing shaft which is located in the lowest position among the plurality of writing shafts by gravity so that the lowest writing shaft can selectively be used. When the writing shaft which has projected is retracted, the engagement with the projection pin is disengaged by depressing the return button provided on the clip, and the writing shaft returns to its original state by a biasing force by the spring. During the operation, the writing shaft moves substantially linearly along the axial direction of the barrel.
In either structure described in the above-described official gazettes, the writing shaft moves substantially linearly along the axial direction of the barrel, however, the circumferential position of each writing shaft basically does not change.
In the structure described in the Japanese Utility Model Laid-Open No. 61-140887, however, since a plurality of knock rods are exposed from the window holes, a problem is that a lot of parts projecting from the barrel deteriorate the appearance of the writing utensil.
In the structure described in the Japanese Utility Model Laid-Open No. 55-47362, a problem is that since it is necessary to operate the return button and entirely change a position of the barrel held by hand in order to switch the writing shaft to be projected, it is troublesome to operate and it is difficult to understand the operation.